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| author | Marc Kleine-Budde <mkl@pengutronix.de> | 2022-05-02 19:54:57 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2022-05-09 18:18:16 +0100 |
| commit | 184434fcd6177b76f929570348935d7c9f22d296 (patch) | |
| tree | bc8e030ca45bcab99bf61a66ae52b44ba1ddc5fc /drivers/spi/spi-imx.c | |
| parent | 07e7593877882fbd07c55b26b7dcf88760449323 (diff) | |
| download | lwn-184434fcd6177b76f929570348935d7c9f22d296.tar.gz lwn-184434fcd6177b76f929570348935d7c9f22d296.zip | |
spi: spi-imx: mx51_ecspi_prepare_message(): skip writing MX51_ECSPI_CONFIG register if unchanged
In mx51_ecspi_prepare_message() the MX51_ECSPI_CONFIG register is
setup for the current spi_message. After writing the register, there
is a delay to ensure that the changes hit the hardware.
This patch checks if the register MX51_ECSPI_CONFIG actually needs to
be changed. If the register content is unchanged the function is left
early, skipping the write to the hardware and the delay. This leads to
a small, but measurable performance increase. For a given workload
with small transfers on an imx6 single core the CPU load decreases
from 30% to ~27%.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20220502175457.1977983-10-mkl@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-imx.c')
| -rw-r--r-- | drivers/spi/spi-imx.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index fe2305e6e38e..bc97337fddf5 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -520,6 +520,7 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx, u32 min_speed_hz = ~0U; u32 testreg, delay; u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG); + u32 current_cfg = cfg; /* set Master or Slave mode */ if (spi_imx->slave_mode) @@ -572,6 +573,9 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx, else cfg &= ~MX51_ECSPI_CONFIG_SSBPOL(spi->chip_select); + if (cfg == current_cfg) + return 0; + writel(cfg, spi_imx->base + MX51_ECSPI_CONFIG); /* |